This invention relates to a sheet conveyance apparatus which may be used in various types of recording equipments, for example, a copier, a printer and the like, (hereinafter referred collectively to as a copying machine), provided with a mechanism in which one-side processed sheets are stored intermediately and from which the one-side processed sheets are conveyed further, and more particularly relates to the improvements relating to a sheet coveyance apparatus which is effective in the case that an image is processed on the both sides of a sheet.
In a copying machine, it is desirable that not only one-side copying operations but also both-side copying operations may be applied to copy sheets. Accordingly, various techniques have so far been proposed to try to materialize the above-mentioned desire. Namely, a set of duplex original documents may be copied on only one side of every copy sheet and also on the both sides thereof by regularly circulating the original document in such a manner, for example, that a set of original document papers to be copied (hereinafter referred simply to as the original), which are printed in the order of pagenation on the both sides of each papers, are fed in the order of the pagenation from a tray onto an original platen through an automatic original feeding means, and is then exposed to light. Every one side of the original is exposed one after another first, and after completing a series of the one-side copying operations, the original for making copy of the other side are fed onto the original platen and are then made them up side down and restored onto the tray again. Besides the above, an original printed on only one side thereof may be copied on the both sides of copy sheets and, it is the matter of course that a copy can be made on only one sides of copy sheets. Such an apparatus as mentioned above can be served as those not only for conveying an original but also for conveying copy sheets. It is further advantageous to use such a document recirculation means applicable to a copying machine as disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 22141/1985.
Now, a conveyance apparatus used for copying an image both side of copy sheets will be described below:
A toner image formed on a photoreceptor drum in a copying section by an optical means is transferred onto a copy sheet fed from a sheet feed tray and is then fixed on it by an image fixing means. Thereafter, when making a copy on only one side of a copy sheet, the copied sheet is delivered and is then collected onto a delivery tray which is normally attached onto a copying machine and is operable from the outside of the machine, in the meantime, when making duplex copies, one-side copied sheets are piled up in an intermediate tray provided inside the machine through a conveyance section.
The one-side copied sheets once piled up there enter into the copying section through a sheet feed conveyor means again, so that a copy may be made on the reverse side of the one side copied sheet and may then be collected onto the delivery tray attached onto the machine through the fixing means.
As for such an apparatus as described above, those described in Japanese Patent O.P.I. Publication No. 82247/1984 are known. There are such a method as described above, in which a series of one-side copies are made altogether first and, after the completion of the one-side copies, a series of the other side copies are then made altogether, and another method in which a one-side copy and the other side copy are made alternatively one after another. There are also some instances where a desired number of both-side copies and one-side copies are made so as to compile a required number.
The techniques mentioned in the last instances are described in Japanese Patent O.P.I. Publication No. 82247/1984, for example.
The technique described in Japanese Patent O.P.I. Publication No. 22141/1985 is that a given number of original document papers such as original manuscripts or copied original papers which are to be copied are stored in a document tray and supplied therefrom one after another so that the every one-side thereof may be copied, and then they are reversed or not reversed to be returned to the document tray again and the both-side copies (or the one-side copies) are finally made, and the original documents or the copied original are restored altogether in the document tray. In this technique, it is not necessary to provide any intermediate tray inbetween. And, Japanese Patent O.P.I. Publication No. 82247/1984 describes a conveyor means used for copy sheets that is one of such a type as those provided separately with a sheet feed tray, a delivery tray and an intermediate tray for reversing and storing copy sheets therebetween.
The former is mainly used for feeding original documents and is made relatively compact. On the other hand, the latter, the above-mentioned conveyor means used for copy sheets, has been inconvenient from the viewpoints of the maintenance and usage, such as that it is apt to take up much room and particularly the conveyor mechanism thereof for conveying the copied sheets into the intermediate tray (hereinafter called a stack tray) and the mechanism for reversing the side of the copied sheets and refeeding them from the stack tray to the copying section have been provided separately so as to become large in size of the apparatus as well as the mechanisms have been complicated and the installation space for the copying machine has accordingly been increased.
Besides the above-mentioned inconveniences, in this type of conveyor means for copy sheets, there have been the other problems such as that, because the path for storing the copy sheets copied one side thereof into a stack tray and the path for refeeding them from the stack tray into the copying section have been provided to the different positions from each other, it has been necessary not only to take much room for providing each of the paths but also to make forward a stopper for supporting the trailing edge of the copy sheets (that is the leading edge thereof in the case of storing them) so as to move the copy sheets upto the position where a refeeding roller is provided, therefore, the constitution of the means has been complicated and many troubles are apt to take place.
The refeeding mechanisms for refeeding the copy sheets from a stack tray into a copying section and for making the both-side copies have so far been provided with a friction wheel as the refeeding roller for feeding the copy sheets and a lifting plate for lifting up the copy sheets stored in the stack tray so as to bring the copy sheets into contact with the friction wheel, wherein the timing for starting the friction wheel in rotation and the timing for starting the lifting plate in lifting motion have been the same. Therefore, at the point of time when bringing the copy sheets into contact with the friction wheel, the friction wheel has already been rotating and, resultantly, the copy sheets had been fed out before the copy sheets have been brought into contact properly with the friction wheel so as to cause a sheet damage.
In the above-mentioned stack tray, it is desired that the copy sheets fed thereinto through a conveyor means are to be so stored therein as to be in such a state that they may readily be fed again. For this purpose, a copy sheet leading edge stopper member and copy sheet width regulating plates have so far been provided to the floor member of the stack tray and, in addition, a means capable of automatically moving and adjusting the leading edge stopper member and the width regulating plates according to the sizes of copy sheets has also been provided. However, the above-mentioned moving means have respectively been equipped with their own independent driving sources, so that the apparatus has been enlarged in size as well as increased in cost.
Further, because the conventional types of the leading edge stopper members have not been equipped with any locking means at all, such stopper members have been shifted from their prescribed positions by the shocks of the copy sheets thereby stopped, so that there have caused the obstacles to the refeed of the copy sheets.
Still further, as described above, a both-side copying apparatus is generally so constructed that a copy is made on one side of copy sheets in a copying section, and the copy sheets are conveyed to the underneath of the copying section and then stored into a stack tray, thereafter the copy sheets are refed from the stack tray into the copying section so as to be copied on the both-side.
In this type of the apparatuses, however, the copy sheets are curled by the heat in the copying and fixing processes and, resultantly, such copy sheets are unable to pass through a conveying path smoothly and are in such a risk that they may be jammed halfway.
The mechanism for changing conveying path in order to store the copy sheets into the stack tray is necessarily provided with at least a function that the copy sheets are made go on to a sheet delivery tray attached onto the machine. In other words, it is necessary for this mechanism to switch a delivering operation for collecting the copy sheet onto the delivery tray or a reversely conveying operation for storing the copy sheet into the stack tray over from one to the other and, therefore, such mechanisms cannot help being complicated and, accordingly, there has also been such a problem in this type of mechanisms that the frequency of causing sheet jamming troubles is inevitably increased.